You must complete and submit an additional information form to HMRC to support new claims for Research and Development (R&D) tax relief, expenditure credit or both.

Your accounting period 

You need to complete an additional information form for each accounting period you’re claiming. 

If you’re claiming for a period of time longer than 12 months, you’ll need to submit: 

• an additional information form for the first 12-month accounting period 
• a further additional information form for the following short accounting period 

For example, if your period of account (the period covered by your accounts) is for 16 months you will make 2 tax returns:

• one covering the first 12 months
• another covering the remaining 4 months

If you wish to make R&D claims for both periods you will need to provide additional information forms for both periods. 

The additional information form for each accounting period should only include information that applies to that accounting period. 

An accounting period can include claims for both R&D tax relief and R&D expenditure credit. If it does, requirements in the following 3 sections apply to each claim separately, not to the accounting period as a whole: 

• qualifying R&D expenditure 
• projects details to include 
• describing each project

When to submit

The additional information form must be submitted before or on the same day you submit the Company Tax Return (CT600). If you do not submit this form, any R&D or expenditure credit claim will not be accepted. 

If this happens:

• we’ll write to you to confirm that we’ll remove your claim for R&D tax relief from your Company Tax Return
• close to the last date for amending the return ― you may not be able to make a valid R&D claim for that accounting period

Who can submit 

You can complete the additional information form if you’re: 

• a representative of the company 
• an agent acting on behalf of the company, using an agent services account 

If you’re an agent 

You must log in to your agent services account before you can complete an additional information form on your client’s behalf. The company should give you their permission to complete the form for them. 

Find out about registering with HMRC for an agent services account.

Company details to include 

To complete the additional information form you’ll need the following details. 

Company details 

Your company’s: 

• Unique Taxpayer Reference (UTR), this must match the one shown in your Company Tax Return 
• employer PAYE reference number 
• VAT registration number 
• business type, for example your current standard industrial classification (SIC) code code

If your company is registered in Northern Ireland, you’ll also need to give the company’s: 

• Company Registration Number (CRN) — this is known as a Company House number or company number (a company registration number is a combination of 8 numbers or 8 alpha-numeric characters and for Northern Ireland the number is NI followed by 6 numbers) 
• registered business address — this is the business address registered with Companies House

Contact details 

The contact details of: 

• the main senior internal R&D contact in the company who is responsible for the R&D claim, for example a company director 
• all agents involved in the R&D claim — including any agent who has given advice, analysed costs, helped prepare technical assessments, given information for or completed the online forms or Company Tax Return

Accounting period start and end date 

You’ll need the start and end date of the accounting period for which you’re claiming. This must match the dates shown in your Company Tax Return.

If you have made an election to use a mean accounting date, you must use the mean start and end dates of the period on both the Additional Information form and the Company Tax Return for the period. If the start and end dates on both submissions do not match, the Additional Information Form will be rejected and the R&D relief claim in the company tax return will be removed.

Companies registered in Northern Ireland

You’ll need to tell us which sector your company is trading in. Depending on the sector, you might be able to opt out of the Northern Ireland provisions.

If you claim enhanced R&D intensive support, your claim cannot exceed the de minimis state aid limit over the 3 years period ending with the day on which the claim is made, or as a result of this claim.

You’ll need to calculate the total de minimis aid received by the undertaking in the 3 years and make a declaration on this form that the de minimis limit has not been exceeded.

You can find out more about enhanced R&D intensive support relief in CIRD125000 – R&D Tax Reliefs: reformed reliefs: ERIS: companies registered in Northern Ireland.

You’ll need to tell us in your claim if you:

• have a trade in goods during the accounting period
• have any relevant activities in relation to electricity during the accounting period - the generation, transmission, distribution, supply, wholesale trade or cross-border exchange of electricity
• do not have a trade in goods or electricity and choose to opt out under Finance Act 2025 section 1112J (4)
• the business or any companies within the group received de minimis state aid in the last 3 years, you will need to calculate the total de minimis aid received and make a declaration that the de minimis limit has not been exceeded

You would also need to declare the amount of additional benefit claimed in this claim period in each sector (agriculture, aquaculture and fishery or other) and make a declaration that this claim will not result in the de minimis limit being exceeded.

For companies registered in Northern Ireland you will be issued a notification of the state aid granted in this ERIS claim.

We’re working to update the additional information form to include the necessary declarations.

If your company would like to submit a claim before the new functions are available, you should continue to use the additional information form. You can do this in the ‘submit a form’ section of this guidance. We will write to you asking you to declare the de minimis amount you are claiming in the current period. We will then send you a notification.

R&D intensity details to include 

You may be able to claim a higher rate of small and medium-sized enterprise (SME) scheme tax credit if you meet the R&D intensity condition. 

If you meet this condition, you’ll need to give details of your: 

• total relevant costs 
• connected companies’ relevant R&D and total costs 
• qualifying R&D expenditure 

Total relevant costs 

You need to include all of the costsrelevant involved in your project.costs.

This includes:

• costs brought into account under generally accepted accounting practice (GAAP) to calculate trade profits, feeding into the profit (loss) before tax position in the profit and loss account or income statement in your GAAP accounts 
• if you’re pre-trading ― any pre-trading costs on which you’ll get relief under section 1045 of Corporation Tax Act 2009, read HMRC manual CIRD90200 
• any amount of capitalised R&D costs on which you’re taking a tax deduction under section 1308 of Corporation Tax Act 2009, read HMRC manual CIRD81450 

It does not include: 

• any amount of amortisation you have to add back in your tax computations because you’re taking or have taken a section 1308 deduction 
• costs on payments or other transfers of value to a connected company 

Connected companies 

You must also include any companies connected to you on at least one day during the accounting period for which the claim covers. 

For more information on connected companies, read HMRC manual CIRD82150.

Qualifying R&D expenditure 

You must include details of the qualifying R&D costs. You can check which costs qualify depending on the relief you’re claiming.

If your project meets the qualifying conditions for R&D, in the Company Tax Return you can claim for: 

• tax relief as a SME 
• expenditure credit as a large company or SME 

If you’re claiming SME tax relief and expenditure credit, you’ll need to provide details of the qualifying costs for your tax relief and expenditure credit claims separately.

You must answer the PAYE cap questions for all SME claims relating to accounting periods beginning on or after 1 April 2021. 

Only companies with an accounting period starting on or after 1 April 2023 have the option of submitting: 

• the number of externally provided workers that have been involved in projects 
• the employer’s PAYE references for all externally provided workers 

This does not prevent companies from claiming costs for externally provided workers in accounting periods that started before 1 April 2023.

SMEs that have a registered office in Northern Ireland

Small and medium-sized enterprises (SMEs) registered in Northern Ireland and claiming the enhanced R&D intensive support (ERIS) are not subject to the restrictions for relief on: 

• payments to overseas contractors
• providers of overseas externally provided workers (EPWs) 

Find out more about R&D Tax Reliefs: reformed reliefs: overseas restrictions. 

Enhanced R&D intensive support relief is de minimis state aid and these claims are subject to a maximum amount of relief over 3 years. The maximum amount varies depending on what sector your company is trading in. 

You will need to calculate the total de minimis aid received by the company and any other company in the group in the 3 years. You must make a declaration on this form that the de minimis limit has not been exceeded. 

You can find out more about enhanced R&D intensive support in CIRD125000 - CIRD125000 – R&D Tax Reliefs: reformed reliefs: ERIS: companies registered in Northern Ireland.

Qualifying indirect activities 

You must include activities which form part of a project but do not directly contribute to the resolution of the scientific or technological uncertainty. 

You can claim for qualifying costs detailed in the ‘Qualifying R&D expenditure’ section of this guidance if they were incurred in certain qualifying indirect activities ― read check what Research and Development (R&D) costs you can claim for more information.

Project details to include 

You need to give us details of the projects you’re claiming for in the accounting period. The details you need to give us depends on the number of projects that you’re claiming for.

If you’re claiming for 1 to 3 projects 

All of the projects are relevant and you need to describe each one you’re claiming for.

If you’re claiming for 4 to 10 projects 

The company must select 3 or more projects to treat as relevant projects. Those projects must together account for at least half of the qualifying expenditure that you’re claiming. 

If you’re claiming for more than 10 projects

The company must select 3 or more projects to treat as relevant projects. Those projects must together account for at least half of the qualifying expenditure that you’re claiming.

But if the company would have to select more than 10 projects to account for at least half of the qualifying expenditure then it should select the 10 projects with the highest qualifying expenditure.

If you’re claiming both SME tax relief and expenditure credit 

You’ll need to provide, separately, details of the required number of projects based on the qualifying costs for your:

• tax relief claim 
• expenditure credit claim 

For example, if you have 8 SME projects and 2 R&D expenditure credit projects, you’ll need to provide project details for:

• SME projects accounting for at least 50% of the total qualifying costs for SME relief, with a minimum of 3 projects described 
• both projects for which you are claiming R&D expenditure credit relief

Describing each project 

The main field of science or technology 

Provide a brief description of the field of science or technology that the project relates to. 

The following terminology will help you complete the description: 

• science ― is the systematic study of the nature and behaviour of the physical and material universe (work in the arts, humanities and social sciences, including economics, is not science for this purpose) 
• technology ― is the practical application of scientific principles or knowledge 

The baseline level of science or technology that the company planned to advance 

Describe the level of knowledge or capability that existed at the time the project started and which the company intended to advance. For example if the intention was to: 

• improve an existing material or device ― describe what its existing features and capabilities were before the project began 
• develop new knowledge in a particular area of science or technology ― describe what was already known before the project began 

The advance in scientific or technological knowledge that the company aims to achieve 

Provide a description of the advance using the baseline level of science or technology the company planned to advance as a comparison. 

The following information will help you complete the description. 

An advance in knowledge or capability in science or technology may have physical consequences or may be an increase in overall knowledge. In either case, a competent professional working in that field would recognise the advance as an significant appreciable improvement. 

The improvements may include: 

• creating a process, material, device, product or service that increases overall knowledge or capability in a field of science or technology 
• significantly improving an existing process, material, device, product or service ― for example to save costs or reduce waste (this refers to genuine non-trivial improvements which result in more than a minor or routine upgrade) 
• using science or technology to copy the effect of a current process, material, device, product or service in a new or improved way

The scientific or technological uncertainties that the company faced 

You must include only scientific or technological uncertainties, for example, the company: 

• does not know if it is possible to create or improve the product or process 
• cannot readily work out how to create or improve the product or process based on what they already know ― for example you tried to build a medical diagnostic tool combining non-invasive testing technology, artificial intelligence (AI) and portability, but you’re not sure about the method to do this 

Your description of the uncertainties should explain: 

• what is stopping you from achieving the advance in scientific or technological knowledge (a problem is not an uncertainty if it can be resolved in a discussion with peers) 
• why it is a technological or scientific uncertainty for the industry, not just your company 
• if a competent professional working in the field would be uncertain as to how to achieve the advance, and explain why

How your project seeks to overcome these uncertainties 

Provide more details about the direct R&D activities used to try and resolve the scientific or technological uncertainties, and the qualifying indirect activities. 

Describe the information in sufficient detail to tell us: 

• how the R&D project was not straightforward 
• the methods planned or used to overcome the uncertainty 
• if the uncertainties were resolved and how or why you’ve been unable to resolve them 

Activities which directly contribute to R&D may include: 

• creating or adapting software, materials or equipment needed to resolve the uncertainty 
• planning activities such as a detailed plan of how you’ll carry out the project 
• designing, testing and analysis to resolve the scientific or technological uncertainty 

Include the qualifying costs incurred on qualifying indirect activities for each project. Check guidance on which R&D costs you can claim for a list of what should be included.

The tax relief you’re claiming and the amount 

Tell us what you’re claiming for and what amount of the qualifying costs applies to each project.

If you want to send us more information 

In addition, you can send us further supporting details about your R&D projects in a separate R&D report, this can include: 

• the claim methodology 
• use of sampling 
• details of the competent professionals 

You can submit the separate R&D report either: 

• by email, using one of the contact us email addresses 
• online, when you complete your Company Tax Return 

Large business customers 

For information on how HMRC deals with expenditure credit claims for large business customers, read HMRC manual CIRD80370. 

If you have any questions about the additional information form, you can contact the Large Business Directorate. You should use the relevant contact us email address and copy in your customer compliance manager (CCM).

Before you start

If you’re: 

• a representative of the company — you’ll need the Government Gateway user ID and password you used when you registered for Corporation Tax, if you do not have a user ID, you can create one the first time you sign in 
• an agent — you’ll need the Government Gateway user ID and password you used when you registered for the agent services account, if you do not have a user ID, you can create one the first time you sign in 

You will not be able to access the form once it’s been submitted, so save a copy before you submit it. 

If you do not have a Government Gateway account, make sure you register for one in good time to receive the details you need to submit your additional information form. 

Each company in the group needs its own Government Gateway account to submit an additional form. You cannot use a ‘Group Tax Manager’ account.

Submit the form

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What you need to do next 

You’ll then get an email to confirm that we’ve received the form. This email will contain a reference number. 

Keep a note of this reference number so that: 

• you can discuss your additional information form with HMRC 
• if we need to, we can check that you’ve submitted your additional information form 

You can then make your claim for R&D tax relief.